For example, Asadikaram et al. (2019) found differences between MDD patients and healthy controls in hormone levels of adrenocorticotropic hormone, testosterone, thyroid–stimulating hormone, free thyroxine index, and cortisol/dehydroepiandrosterone sulfate (DHEA–S), while others consider vasopressin and oxytocin to play a pivotal role in MDD etiology (for a review, see Iovino et al., 2018). Here, OXT is linked to major depressive disorder.